The present invention relates to a power sander, and more particularly to a sander which has a sanding plate which conducts movements in parallelism with a support surface thereof, and in which a plurality of sanding elements, such as sandpaper elements, can be interchangeably mounted on the sanding plate so as to be supported on and cover the support surface of the sanding plate.
There are already known various types of the sanders of the type here under consideration, and in most of such constructions of sanders a clamping arrangement is mounted on the sanding plate for pivoting between an engaging and a disengaging position, the clamping arrangement being urged toward the engaging position thereof in which a clamping portion of the clamping arrangement clamps the sanding element to the sanding plate. As long as the clamping arrangement is readily accessible to the user of the sander, no problems arise with exchanging a worn-out sanding element for a fresh one, or with exchanging a sanding element for a different sanding element of a different coarseness.
However, such sanders in which the clamping arrangement is readily accessible suffer of an important disadvantage which is to be seen in the fact that the access of the user of the sander to the clamping arrangement must not be impeded by various parts of the sander, such as a casing which surrounds the sanding plate and prevents dust produced during the sanding operation from being freely discharged into the ambient atmosphere.
In order to prevent such discharge of the sanding dust into the ambient atmosphere, it has already been proposed to provide a casing which surrounds the sanding plate at all sides thereof except for the support surface thereof which casing, together with the surface being acted upon by the sander, bound an almost completely enclosed space from which it is difficult for the dust to escape. It has been further proposed to maintain the interior of the casing at a subatmospheric pressure, whereby air is drawn through the gap between the casing and the surface which is acted upon so that the dust originating during the sanding operation is effectively prevented from escaping outwardly of the casing, is entrained in the air flowing through the gap, and is withdrawn from the interior space of the casing and accumulated in a storage receptacle to be later discarded. Usually, the sanders of this type include a cover plate which extends parallel to the sanding plate, and a collar-shaped element which circumferentially surrounds the sanding plate with spacing therefrom. In such sanders, the collar-shaped element is detachably mounted on the cover plate, the primary reason for detachably mounting the collar-shaped element on the cover plate being the fact that the collar-shaped element must be removed in order to gain access to the clamping arrangement whenever a sanding element is to be exchanged for a different one. In addition to the disadvantage which results from the need for removing the collar-shaped element prior to exchange of the sanding element, and for reattaching the collar-shaped element after the exchange of the sanding element, a further disadvantage is to be seen in the fact that the space between the cover plate and the sanding plate is usually very small, so that it is rather difficult to pivot the clamping arrangement into the disengaging position thereof against the force of a relatively strong spring which urges the clamping arrangement toward the clamping or engaging position thereof.